This proposal addresses central oxytocinergic mechanisms underlying the interactions of affective behaviors, neuroendocrine function, and autonomic activity by investigating the effects of social isolation in female prairie voles. This research is directly relevant to health issues such as social behavior, depression, anxiety, and heart disease. Study 1 employs radioimmunoassay, enzyme immunoassay, and immunocytochemistry to investigate the time course of hormone changes in plasma and hypothalamic brain tissue following social isolation in voles (Aim 1). Study 2 examines depression- and anxiety-like behaviors and endocrine function, and uses radiotelemetry to measure autonomic parameters, in response to social isolation (Aim 2). Study 3 investigates specific oxytocinergic mechanisms that might underlie stressor-induced changes by examining central (intracerebroventricular) administration of oxytocin and/or an oxytocin antagonist to alter the behavioral, neuroendocrine, and autonomic responses to social isolation (Aim 3). The present research will enhance our understanding of how the social environment impacts behavior, physiology, and brain function, and can aid in developing new treatments for patients with affective disorders and cardiovascular disease. [unreadable] [unreadable]